Charges are expected to be laid after the driver involved in a fatal NSW coach crash was arrested.

The coach rolled into the Hunter Valley, killing 10 people and injuring another 25 at 11.30pm on Sunday night.

Taylor Ryan, a reporter from Australia's 10 News says investigations are still in the early stages, and police have only just rolled the coach upright.

"Now that it's upright, I think they'll be able to get a better idea of exactly what they're dealing with and what might have been the cause of the crash. At this stage, all we know is that the bus has picked up around 40 people."

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